Impacts of elevated CO2 on expression of plant defensive compounds in Bt-transgenic cotton in response to infestation by cotton bollworm

Abstract

1 The allocation of defensive compounds of transgenic Bt (cv. GK-12) and nontransgenic cotton (cv. Simian-3) grown in elevated CO2 in response to infestation by cotton bollworm Helicoverpa armigera (Hübner) was studied in closed-dynamics CO2 chambers. 2 A significant reduction in foliar nitrogen content and Bt toxin protein occurred when transgenic Bt cotton grew under elevated CO2. A significantly higher carbon/nitrogen ratio as well as condensed tannin and gossypol contents was observed for transgenic Bt (cv. GK-12) and nontransgenic cotton in elevated CO2, in partial support of the carbon nutrient balance hypothesis as a result of limiting nitrogen and excess carbon in cotton plants in response to elevated CO2. 3 The CO2 level and infestation time significantly affected the foliar nitrogen, condensed tannin, gossypol and Bt toxin protein contents of cotton plants after feeding by H. armigera. The interaction between CO2 levels × cotton variety had a significant effect on foliar nitrogen content after injury by H. armigera.